diff --git a/source/index.rst b/source/index.rst
index 166505ebb..b6f7398d9 100644
--- a/source/index.rst
+++ b/source/index.rst
@@ -16,7 +16,7 @@ for creating parallel applications:
 
 .. toctree::
    :hidden:
-   :maxdepth: 3
+   :maxdepth: 4
 
    introduction
    architecture